/*
 * Copyright 2013, 2014 Megion Research and Development GmbH
 *
 * Licensed under the Microsoft Reference Source License (MS-RSL)
 *
 * This license governs use of the accompanying software. If you use the software, you accept this license.
 * If you do not accept the license, do not use the software.
 *
 * 1. Definitions
 * The terms "reproduce," "reproduction," and "distribution" have the same meaning here as under U.S. copyright law.
 * "You" means the licensee of the software.
 * "Your company" means the company you worked for when you downloaded the software.
 * "Reference use" means use of the software within your company as a reference, in read only form, for the sole purposes
 * of debugging your products, maintaining your products, or enhancing the interoperability of your products with the
 * software, and specifically excludes the right to distribute the software outside of your company.
 * "Licensed patents" means any Licensor patent claims which read directly on the software as distributed by the Licensor
 * under this license.
 *
 * 2. Grant of Rights
 * (A) Copyright Grant- Subject to the terms of this license, the Licensor grants you a non-transferable, non-exclusive,
 * worldwide, royalty-free copyright license to reproduce the software for reference use.
 * (B) Patent Grant- Subject to the terms of this license, the Licensor grants you a non-transferable, non-exclusive,
 * worldwide, royalty-free patent license under licensed patents for reference use.
 *
 * 3. Limitations
 * (A) No Trademark License- This license does not grant you any rights to use the Licensor’s name, logo, or trademarks.
 * (B) If you begin patent litigation against the Licensor over patents that you think may apply to the software
 * (including a cross-claim or counterclaim in a lawsuit), your license to the software ends automatically.
 * (C) The software is licensed "as-is." You bear the risk of using it. The Licensor gives no express warranties,
 * guarantees or conditions. You may have additional consumer rights under your local laws which this license cannot
 * change. To the extent permitted under your local laws, the Licensor excludes the implied warranties of merchantability,
 * fitness for a particular purpose and non-infringement.
 */

package cy.agorise.graphenej.crypto;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;


public class AndroidRandomSource implements RandomSource, EntropySource {

    @Override
    public synchronized void nextBytes(byte[] bytes) {
        // On Android we use /dev/urandom for providing random data
        File file = new File("/dev/urandom");
        if (!file.exists()) {
            throw new RuntimeException("Unable to generate random bytes on this Android device");
        }
        try {
            FileInputStream stream = new FileInputStream(file);
            DataInputStream dis = new DataInputStream(stream);
            dis.readFully(bytes);
            dis.close();
        } catch (IOException e) {
            throw new RuntimeException("Unable to generate random bytes on this Android device", e);
        }
    }

    @Override
    public ByteBuffer provideEntropy() {
        byte[] buffer = new byte[ 256 / 8];
        nextBytes(buffer);
        ByteBuffer byteBuffer = ByteBuffer.allocate(buffer.length);
        byteBuffer.put(buffer, 0, buffer.length);
        return byteBuffer;
    }
}
